Investigation on the effective remediation of quinoline at solid/solution interface using modified agricultural waste: an inclusive study

This research work explores the potential of modified agricultural waste for the sorption of quinoline from aqueous media. A quinoline removal efficiency of around 97 % and sorption capacities of ~20 (batch) and ~35 mg g^?1 (fixed-bed) were achieved. Pseudo-second-order kinetics and Temkin isotherm best represented the equilibrium sorption data. The sorption of quinoline is exothermic and spontaneous in nature with a slight increase in the system entropy. The quinoline sorption mechanism is controlled by H-bonding, π–π dispersive interactions, boundary layer, and intraparticle diffusion. Microwave–chemical integrated regeneration technique retrieves the sorption capacity of the exhausted sorbent with 99.15, 97.64, and 95.55 % of the original, in three sorption–regeneration cycles. Energy recovery (19.365 MJ kg^?1) from the quinoline-loaded sorbent and the potential utilization of left-over ash materials enhanced the prospective of the sorbent for the remediation of pollutants for a clean and green environment.     

Sources of salinity and arsenic in groundwater in southwest Bangladesh

Background

High salinity and arsenic (As) concentrations in groundwater are widespread problems in the tidal deltaplain of southwest Bangladesh. To identify the sources of dissolved salts and As, groundwater samples from the regional shallow Holocene aquifer were collected from tubewells during the dry (May) and wet (October) seasons in 2012–2013. Thirteen drill cores were logged and 27 radiocarbon ages measured on wood fragments to characterize subsurface stratigraphy.

Results

Drill cuttings, exposures in pits and regional studies reveal a >5 m thick surface mud cap overlying a ~30 m thick upper unit of interbedded mud and fine sand layers, and a coarser lower unit up to 60 m thick dominated by clean sands, all with significant horizontal variation in bed continuity and thickness. This thick lower unit accreted at rates of ~2 cm/year through the early Holocene, with local subsidence or compaction rates of 1–3 mm/year. Most tubewells are screened at depths of 15–52 m in sediments deposited 8000–9000 YBP. Compositions of groundwater samples from tubewells show high spatial variability, suggesting limited mixing and low and spatially variable recharge rates and flow velocities. Groundwaters are Na–Cl type and predominantly sulfate-reducing, with specific conductivity (SpC) from 3 to 29 mS/cm, high dissolved organic carbon (DOC) 11–57 mg/L and As 2–258 ug/L, and low sulfur (S) 2–33 mg/L.

Conclusions

Groundwater compositions can be explained by burial of tidal channel water and subsequent reaction with dissolved organic matter, resulting in anoxia, hydrous ferric oxide (HFO) reduction, As mobilization, and sulfate (SO₄) reduction and removal in the shallow aquifer. Introduction of labile organic carbon in the wet season as rice paddy fertilizer may also cause HFO reduction and As mobilization. Variable modern recharge occurred in areas where the clay cap pinches out or is breached by tidal channels, which would explain previously measured ¹⁴C groundwater ages being less than depositional ages. Of samples collected from the shallow aquifer, Bangladesh Government guidelines are exceeded in 46 % for As and 100 % for salinity.

     

Investigation of influence of tunneling on existing building and tunnel: model tests and numerical simulations

To investigate the realistic ground behavior during tunneling, a new device has been developed. With the new device, model tests of tunnel excavation considering an existing tunnel and an existing building were carried out. Non-linear finite element analyses corresponding to the model tests were also conducted using FEMtij-2D software where an elastoplastic subloading t _ij model was used to describe the mechanical behavior of soil. Earth pressure distribution around the tunnels and ground movements during tunnel excavation depend on the distance and position between the twin tunnels. There is a significant effect of tunneling on the existing foundation of building even in the case where the tunnel is constructed in deep underground. The numerical analyses capture well the results of the model tests.     

Water and sediment quality parameters in the Chalan Beel,the largest wetland of Bangladesh

A study was conducted to investigate the status of the water and sediment quality in the Chalan Beel——a major fresh water fish reservoir of the country for a period of one year from July 2007 to June 2008. The mean values of water quality parameters(depth: 214.73±152.22 cm, temperature 27.68±4.26℃, transparency 123±82 cm, p H 9.7±0.47, total alkalinity 137±42 mg/L, conductivity 307±147 μs/cm, total dissolved solids 183±89 mg/L, ammonia-N 0.27±0.39 mg/L, nitrate-N 0.09±0.07 mg/L, phosphate-P 2.01±2.53 mg/L) and sediment quality parameters(p H 7.21±0.35, organic matter 2.59±0.52%, total nitrogen 0.09±0.04%, available phosphorus 5.4±3.6 Meq./100 g and exchangeable potassium 0.43±0.14 Meq./100 g) were within the range recommended for most of the inland fishes of Bangladesh. Although the water and sediment quality parameters except ammonia and phosphate are in the suitable range, the overall results suggest that better management techniques should be practiced in order to overcome the declining trend of associated aquatic life(fauna and flora) of this important fresh water body of Bangladesh.     

Spatiotemporal trends of temperature extremes in Bangladesh under changing climate using multi-statistical techniques

Theoretical and Applied Climatology - The rise in the frequency and magnitude of extreme temperature phenomena across the globe has led to the recurrent incidence of global climate hazards, which...     

Assessment of Land Surface Subsidence Due to Underground Metal Mining Using Integrated Spaceborne Repeat-Pass Differential Interferometric Synthetic Aperture Radar (DInSAR) Technique and Ground Based Observations

Differential interferometric synthetic aperture radar (DInSAR) is a novel remote sensing technique to measure earth surface deformation. It is capable of obtaining dense information related to the deformation of a large area efficiently, economically and effectively. Therefore, DInSAR is a promising technology for monitoring the earth surface deformation related to some natural hazardous events, such as earthquake, volcano eruption, land subsidence, landslide. In present study, Conventional DInSAR technique have been applied to a mineral rich zone, coming under the Khetri copper belt, a part of Northern Aravali range of hillocks in India, predominant with mining activities since late 1960’s to address the possibility of deformation phenomena due to hard rock underground metal mining. Four interferometric SAR data sets of Radarsat-2 was used for the study area to address the subsidence/uplift phenomena. Further, results obtained from conventional DInSAR technique using Radarsat-2 data sets compared with results obtained from ground based observation technique for its validity. In both the techniques, deformation results obtained in terms of average subsidence rate in mm (quarterly basis) of points under study within mining zone of Mine-A has well agreed to each other. Further, it has been observed that average subsidence rate in mm (quarterly basis) obtained from space based observation and ground based observation are 5.6 and 6.67, respectively over the points under study in mining zone of Mine-A.     

Sitnikov restricted four-body problem with radiation pressure

An analytical study of the elliptic Sitnikov restricted four-body problem when all the primaries as source of same radiation pressure is presented. We find a solution, which is valid for small bounded oscillations in case of moderate eccentricity of the primary. We have linearized the equation of motion to obtain the Hill’s type equation. Using the Courant and Snyder transformation, Hill’s equation transformed into harmonic oscillator type equation. We have used the Lindstedt-Poincare perturbation method and again we have applied the Courant and Snyder transformation to obtain the final result.